Data types

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Revision as of 03:50, 24 February 2024 by LassiPulkkinen (talk | contribs) (Add BitSet to the table of definitions. Document Fixed BitSet.)
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This article defines the data types used in the protocol. All data sent over the network (except for VarInt and VarLong) is big-endian, that is the bytes are sent from most significant byte to least significant byte. The majority of everyday computers are little-endian, therefore it may be necessary to change the endianness before sending data over the network.

Definitions

Name Size (bytes) Encodes Notes
Boolean 1 Either false or true True is encoded as 0x01, false as 0x00.
Byte 1 An integer between -128 and 127 Signed 8-bit integer, two's complement
Unsigned Byte 1 An integer between 0 and 255 Unsigned 8-bit integer
Short 2 An integer between -32768 and 32767 Signed 16-bit integer, two's complement
Unsigned Short 2 An integer between 0 and 65535 Unsigned 16-bit integer
Int 4 An integer between -2147483648 and 2147483647 Signed 32-bit integer, two's complement
Long 8 An integer between -9223372036854775808 and 9223372036854775807 Signed 64-bit integer, two's complement
Float 4 A single-precision 32-bit IEEE 754 floating point number
Double 8 A double-precision 64-bit IEEE 754 floating point number
String (n) ≥ 1
≤ (n×3) + 3 		A sequence of Unicode scalar values UTF-8 string prefixed with its size in bytes as a VarInt. Maximum length of n characters, which varies by context. The encoding used on the wire is regular UTF-8, not Java's "slight modification". However, the length of the string for purposes of the length limit is its number of UTF-16 code units, that is, scalar values > U+FFFF are counted as two. Up to n × 3 bytes can be used to encode a UTF-8 string comprising n code units when converted to UTF-16, and both of those limits are checked. Maximum n value is 32767. The + 3 is due to the max size of a valid length VarInt.
Text Component Varies See Text formatting#Text components Encoded as a NBT Tag, with the type of tag used depending on the case:
  • As a nameless String Tag: For components only containing text (no styling, no events etc.).
  • As a Compound Tag: Every other case.
JSON Text Component ≥ 1
≤ (262144×3) + 3 		See Text formatting#Text components Encoded as a String with max length of 262144.
Identifier ≥ 1
≤ (32767×3) + 3 		See Identifier below Encoded as a String with max length of 32767.
VarInt ≥ 1
≤ 5 		An integer between -2147483648 and 2147483647 Variable-length data encoding a two's complement signed 32-bit integer; more info in their section
VarLong ≥ 1
≤ 10 		An integer between -9223372036854775808 and 9223372036854775807 Variable-length data encoding a two's complement signed 64-bit integer; more info in their section
Entity Metadata Varies Miscellaneous information about an entity See Entity_metadata#Entity Metadata Format
Slot Varies An item stack in an inventory or container See Slot Data
NBT Tag Varies Depends on context See NBT
Position 8 An integer/block position: x (-33554432 to 33554431), z (-33554432 to 33554431), y (-2048 to 2047) x as a 26-bit integer, followed by z as a 26-bit integer, followed by y as a 12-bit integer (all signed, two's complement). See also the section below.
Angle 1 A rotation angle in steps of 1/256 of a full turn Whether or not this is signed does not matter, since the resulting angles are the same.
UUID 16 A UUID Encoded as an unsigned 128-bit integer (or two unsigned 64-bit integers: the most significant 64 bits and then the least significant 64 bits)
BitSet Varies See #BitSet below A length-prefixed bit set.
Fixed BitSet (n) n See #Fixed BitSet below A bit set with a fixed length of n bytes.
Optional X 0 or size of X A field of type X, or nothing Whether or not the field is present must be known from the context.
Array of X count times size of X Zero or more fields of type X The count must be known from the context.
X Enum size of X A specific value from a given list The list of possible values and how each is encoded as an X must be known from the context. An invalid value sent by either side will usually result in the client being disconnected with an error or even crashing.
Byte Array Varies Depends on context This is just a sequence of zero or more bytes, its meaning should be explained somewhere else, e.g. in the packet description. The length must also be known from the context.

Identifier

Identifiers are a namespaced location, in the form of minecraft:thing. If the namespace is not provided, it defaults to minecraft (i.e. thing is minecraft:thing). Custom content should always be in its own namespace, not the default one. Both the namespace and value can use all lowercase alphanumeric characters (a-z and 0-9), dot (.), dash (-), and underscore (_). In addition, values can use slash (/). The naming convention is lower_case_with_underscores. More information. For ease of determining whether a namespace or value is valid, here are regular expressions for each:

  • Namespace: [a-z0-9.-_]
  • Value: [a-z0-9.-_/]

VarInt and VarLong

Variable-length format such that smaller numbers use fewer bytes. These are very similar to Protocol Buffer Varints: the 7 least significant bits are used to encode the value and the most significant bit indicates whether there's another byte after it for the next part of the number. The least significant group is written first, followed by each of the more significant groups; thus, VarInts are effectively little endian (however, groups are 7 bits, not 8).

VarInts are never longer than 5 bytes, and VarLongs are never longer than 10 bytes. Within these limits, unnecessarily long encodings (e.g. 81 00 to encode 1) are allowed.

Pseudocode to read and write VarInts and VarLongs: 

private static final int SEGMENT_BITS = 0x7F;
private static final int CONTINUE_BIT = 0x80;

public int readVarInt() {
    int value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 32) throw new RuntimeException("VarInt is too big");
    }

    return value;
}

public long readVarLong() {
    long value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (long) (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 64) throw new RuntimeException("VarLong is too big");
    }

    return value;
}

public void writeVarInt(int value) {
    while (true) {
        if ((value & ~SEGMENT_BITS) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

public void writeVarLong(long value) {
    while (true) {
        if ((value & ~((long) SEGMENT_BITS)) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

Warning.png Note Minecraft's VarInts are identical to LEB128 with the slight change of throwing a exception if it goes over a set amount of bytes.

Warning.png Note that Minecraft's VarInts are not encoded using Protocol Buffers; it's just similar. If you try to use Protocol Buffers Varints with Minecraft's VarInts, you'll get incorrect results in some cases. The major differences:

  • Minecraft's VarInts are all signed, but do not use the ZigZag encoding. Protocol buffers have 3 types of Varints: uint32 (normal encoding, unsigned), sint32 (ZigZag encoding, signed), and int32 (normal encoding, signed). Minecraft's are the int32 variety. Because Minecraft uses the normal encoding instead of ZigZag encoding, negative values always use the maximum number of bytes.
  • Minecraft's VarInts are never longer than 5 bytes and its VarLongs will never be longer than 10 bytes, while Protocol Buffer Varints will always use 10 bytes when encoding negative numbers, even if it's an int32.

Sample VarInts:

Value Hex bytes Decimal bytes
0 0x00 0
1 0x01 1
2 0x02 2
127 0x7f 127
128 0x80 0x01 128 1
255 0xff 0x01 255 1
25565 0xdd 0xc7 0x01 221 199 1
2097151 0xff 0xff 0x7f 255 255 127
2147483647 0xff 0xff 0xff 0xff 0x07 255 255 255 255 7
-1 0xff 0xff 0xff 0xff 0x0f 255 255 255 255 15
-2147483648 0x80 0x80 0x80 0x80 0x08 128 128 128 128 8

Sample VarLongs:

Value Hex bytes Decimal bytes
0 0x00 0
1 0x01 1
2 0x02 2
127 0x7f 127
128 0x80 0x01 128 1
255 0xff 0x01 255 1
2147483647 0xff 0xff 0xff 0xff 0x07 255 255 255 255 7
9223372036854775807 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x7f 255 255 255 255 255 255 255 255 127
-1 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x01 255 255 255 255 255 255 255 255 255 1
-2147483648 0x80 0x80 0x80 0x80 0xf8 0xff 0xff 0xff 0xff 0x01 128 128 128 128 248 255 255 255 255 1
-9223372036854775808 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x01 128 128 128 128 128 128 128 128 128 1

Position

Note: What you are seeing here is the latest version of the Data types article, but the position type was different before 1.14.

64-bit value split into three signed integer parts:

  • x: 26 MSBs
  • z: 26 middle bits
  • y: 12 LSBs

For example, a 64-bit position can be broken down as follows:

Example value (big endian): 01000110000001110110001100 10110000010101101101001000 001100111111

  • The red value is the X coordinate, which is 18357644 in this example.
  • The blue value is the Z coordinate, which is -20882616 in this example.
  • The green value is the Y coordinate, which is 831 in this example.

Encoded as follows: 

((x & 0x3FFFFFF) << 38) | ((z & 0x3FFFFFF) << 12) | (y & 0xFFF)

And decoded as: 

val = read_long();
x = val >> 38;
y = val << 52 >> 52;
z = val << 26 >> 38;

Note: The above assumes that the right shift operator sign extends the value (this is called an arithmetic shift), so that the signedness of the coordinates is preserved. In many languages, this requires the integer type of val to be signed. In the absence of such an operator, the following may be useful: 

if x >= 1 << 25 { x -= 1 << 26 }
if y >= 1 << 11 { y -= 1 << 12 }
if z >= 1 << 25 { z -= 1 << 26 }

Fixed-point numbers

Some fields may be stored as fixed-point numbers, where a certain number of bits represents the signed integer part (number to the left of the decimal point) and the rest represents the fractional part (to the right). Floating points (float and double), in contrast, keep the number itself (mantissa) in one chunk, while the location of the decimal point (exponent) is stored beside it.

Essentially, while fixed-point numbers have lower range than floating points, their fractional precision is greater for higher values. This makes them ideal for representing global coordinates of an entity in Minecraft, as it's more important to store the integer part accurately than position them more precisely within a single block (or meter).

Coordinates are often represented as a 32-bit integer, where 5 of the least-significant bits are dedicated to the fractional part, and the rest store the integer part.

Java lacks support for fractional integers directly, but you can represent them as integers. To convert from a double to this integer representation, use the following formulas: 

 abs_int = (int) (double * 32.0D);

And back again: 

 double = (double) (abs_int / 32.0D);

Particle

Particle Name Particle ID Data
minecraft:ambient_entity_effect 0 None
minecraft:angry_villager 1 None
minecraft:block 2
Field Name Field Type Meaning
BlockState VarInt The ID of the block state.
minecraft:block_marker 3
Field Name Field Type Meaning
BlockState VarInt The ID of the block state.
minecraft:bubble 4 None
minecraft:cloud 5 None
minecraft:crit 6 None
minecraft:damage_indicator 7 None
minecraft:dragon_breath 8 None
minecraft:dripping_lava 9 None
minecraft:falling_lava 10 None
minecraft:landing_lava 11 None
minecraft:dripping_water 12 None
minecraft:falling_water 13 None
minecraft:dust 14
Field Name Field Type Meaning
Red Float The red RGB value, between 0 and 1. Divide actual RGB value by 255.
Green Float The green RGB value, between 0 and 1. Divide actual RGB value by 255.
Blue Float The blue RGB value, between 0 and 1. Divide actual RGB value by 255.
Scale Float The scale, will be clamped between 0.01 and 4.
minecraft:dust_color_transition 15
Field Name Field Type Meaning
From Red Float The start red RGB value, between 0 and 1. Divide actual RGB value by 255.
From Green Float The start green RGB value, between 0 and 1. Divide actual RGB value by 255.
From Blue Float The start blue RGB value, between 0 and 1. Divide actual RGB value by 255.
Scale Float The scale, will be clamped between 0.01 and 4.
To Red Float The end red RGB value, between 0 and 1. Divide actual RGB value by 255.
To Green Float The end green RGB value, between 0 and 1. Divide actual RGB value by 255.
To Blue Float The end blue RGB value, between 0 and 1. Divide actual RGB value by 255.
minecraft:effect 16 None
minecraft:elder_guardian 17 None
minecraft:enchanted_hit 18 None
minecraft:enchant 19 None
minecraft:end_rod 20 None
minecraft:entity_effect 21 None
minecraft:explosion_emitter 22 None
minecraft:explosion 23 None
minecraft:gust 24 None
minecraft:gust_emitter 25 None
minecraft:sonic_boom 26 None
minecraft:falling_dust 27
Field Name Field Type Meaning
BlockState VarInt The ID of the block state.
minecraft:firework 28 None
minecraft:fishing 29 None
minecraft:flame 30 None
minecraft:cherry_leaves 31 None
minecraft:sculk_soul 32 None
minecraft:sculk_charge 33
Field Name Field Type Meaning
Roll Float How much the particle will be rotated when displayed.
minecraft:sculk_charge_pop 34 None
minecraft:soul_fire_flame 35 None
minecraft:soul 36 None
minecraft:flash 37 None
minecraft:happy_villager 38 None
minecraft:composter 39 None
minecraft:heart 40 None
minecraft:instant_effect 41 None
minecraft:item 42
Field Name Field Type Meaning
Item Slot The item that will be used.
minecraft:vibration 43
Field Name Field Type Meaning
Position Source Type VarInt The type of the vibration source (0 for `minecraft:block`, 1 for `minecraft:entity`)
Block Position Position The position of the block the vibration originated from. Only present if Position Type is minecraft:block.
Entity ID VarInt The ID of the entity the vibration originated from. Only present if Position Type is minecraft:entity.
Entity eye height Float The height of the entity's eye relative to the entity. Only present if Position Type is minecraft:entity.
Ticks VarInt The amount of ticks it takes for the vibration to travel from its source to its destination.
minecraft:item_slime 44 None
minecraft:item_snowball 45 None
minecraft:large_smoke 46 None
minecraft:lava 47 None
minecraft:mycelium 48 None
minecraft:note 49 None
minecraft:poof 50 None
minecraft:portal 51 None
minecraft:rain 52 None
minecraft:smoke 53 None
minecraft:white_smoke 54 None
minecraft:sneeze 55 None
minecraft:spit 56 None
minecraft:squid_ink 57 None
minecraft:sweep_attack 58 None
minecraft:totem_of_undying 59 None
minecraft:underwater 60 None
minecraft:splash 61 None
minecraft:witch 62 None
minecraft:bubble_pop 63 None
minecraft:current_down 64 None
minecraft:bubble_column_up 65 None
minecraft:nautilus 66 None
minecraft:dolphin 67 None
minecraft:campfire_cosy_smoke 68 None
minecraft:campfire_signal_smoke 69 None
minecraft:dripping_honey 70 None
minecraft:falling_honey 71 None
minecraft:landing_honey 72 None
minecraft:falling_nectar 73 None
minecraft:falling_spore_blossom 74 None
minecraft:ash 75 None
minecraft:crimson_spore 76 None
minecraft:warped_spore 77 None
minecraft:spore_blossom_air 78 None
minecraft:dripping_obsidian_tear 79 None
minecraft:falling_obsidian_tear 80 None
minecraft:landing_obsidian_tear 81 None
minecraft:reverse_portal 82 None
minecraft:white_ash 83 None
minecraft:small_flame 84 None
minecraft:snowflake 85 None
minecraft:dripping_dripstone_lava 86 None
minecraft:falling_dripstone_lava 87 None
minecraft:dripping_dripstone_water 88 None
minecraft:falling_dripstone_water 89 None
minecraft:glow_squid_ink 90 None
minecraft:glow 91 None
minecraft:wax_on 92 None
minecraft:wax_off 93 None
minecraft:electric_spark 94 None
minecraft:scrape 95 None
minecraft:shriek 96
Field Name Field Type Meaning
Delay VarInt The time in ticks before the particle is displayed
minecraft:egg_crack 97 None
minecraft:dust_plume 98 None
minecraft:gust_dust 99 None
minecraft:trial_spawner_detection 100 None

Bit sets

The types BitSet and Fixed BitSet represent packed lists of bits. The Notchian implementation uses Java's BitSet class.

BitSet

Bit sets of type BitSet are prefixed by their length in longs.

Field Name Field Type Meaning
Length VarInt Number of longs in the following array. May be 0 (if no bits are set).
Data Array of Long A packed representation of the bit set as created by BitSet.toLongArray.

The ith bit is set when (Data[i / 64] & (1 << (i % 64))) != 0, where i starts at 0.

Fixed BitSet

Bit sets of type Fixed BitSet (n) have a fixed length of n bytes. Note that this is different from BitSet, which uses longs.

Field Name Field Type Meaning
Data Byte Array (n) A packed representation of the bit set as created by BitSet.toByteArray.

The ith bit is set when (Data[i / 8] & (1 << (i % 8))) != 0, where i starts at 0. This encoding is not equivalent to the long array in BitSet.

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